Blockout mechanism for pushbutton switch



6, 1968 J. H. WILLIAMS 3,395,590

BLOCKOUT MECHANISM FOR PUSHBUTTON SWITCH Filed April 15, 1966 h FIG-7 INVENTOR JOHN H. WILLIAMS fifi-JLL-v, Ll/lgm, 014.0 BY 4W4 4m and ATTORNEYS United States Patent 3,395,590 BLOCKOUT MECHANISM FOR PUSHBUTTON SWITCH John H. Williams, Barrington, Ill., assignor to Oak Electro/Netics Corp., a corporation of Delaware Filed Apr. 15, 1966, Ser. No. 542,914 8 Claims. (Cl. 74-483) ABSTRACT OF THE DISCLOSURE A blockout mechanism for a pushbutton assembly in which a plurality of groups of pushbuttons each operate a pushrod for reciprocating movement. A first blockout mechanism is provided for each group of pushrods to permit only one pushbutton in a single group to be fully depressed at a time. A connecting means is provided for each group of pushrods and the connecting means is actuated when a pushbutton is depressed in the respective group. A second blockout mechanism independent of the first blockout mechanism is provided to permit only one connecting means to be actuated at a time so that the two blockout mechanisms and the connecting means cooperate to permit only one pushbutton in the entire pushbutton assembly to be fully depressed at a time. Each blockout mechanism comprises a plurality of blockout members positioned end-to-end and each blockout member has an abutting surface which overlaps with the abutting surface of each adjacent blockout member.

It is common to provide blockout mechanisms for pushbutton switches to permit actuation of only one pushbutton at a time. This is usually accomplished by means of blockout members such as malls, discs, slides or the like placed side-by-side in a row in a closed end channel. The blockout members are in registry with a row of pushrods with only sufficient clearance between the members for one pushrod to pass therethrough. In the conventional blockout system, the number of pushrods that can be blocked out is limited by the accumulated tolerance of five times the unit tolerance.

The blockout of this invention completely divorces the accumulated tolerance of a single row of blockout members from that of any other row, by employing a treadle bar with each row of pushbuttons, the treadle bar being actuated by the pushrods in that row and being independent of the blockout members of the respective row. An independent or universal row of second blockout members extends transversely across all the rows and is contacted by all of the treadle bars allowing only one treadle bar at a time to be fully operated. This construction makes possible the blocking out of a far greater number of .pushbuttons, since the total accumulated tolerance of the blockout members is only that in a single row, or, the accumulated tolerance in the universal row of blockout members actuated by the treadle bars of each row.

In addition, this invention includes unique blockout members which greatly increase the total permissible accumulated tolerance in any single row thereof. Heretofore, practice has shown that forty-eight is the normal maximum limit of abutting type blockout members. Beyond this maximum. the accumulated tolerance between the blockout members would permit more than one pushrod to be depressed at a time. The device of this invention includes blockout members having overlapping portions which require that the blockout members be displaced a greater distance by the pushrods, resulting in a greater permissible accumulated tolerance in any single row of blockout members.

Therefore, one object of this invention is to provide a new and improved blockout mechanism for pushbutton assemblies.

Another object of this invention is to divorce the action of the blockout members in a single row of pushbuttons from the action of the blockout members of any other row of pushbuttons by employing an independent universal row of blockout members actuated by a treadle bar in each row of pushrods.

A further object of this invention is to provide new and improved blockout members which allow an unlimited number of pushbuttons in a single row thereof by increasing the permissible accumulated tolerance of the blockout members.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of a switch apparatus embodying the invention;

FIG. 2 is a side elevation view of a pushbutton assembly embodying the invention, with all of the pushbuttons in their elevated inoperative position, and with portions of the device cut away to facilitate the illustration;

FIG. 3 is a side elevation view as in FIG. 2, illustrating one of the pushbuttons in its depressed operative position;

FIG. 4 is an end elevation view of the pushbutton assembly with portions thereof cut away to facilitate the illustration;

FIG. 5 is a partial sectional view on an enlarged scale illustrating the locking and releasing means for the pushrods;

FIG. 6 is a partial elevation view on an enlarged scale of the blockout members of this invention; and

FIG. 7 is a plan view of the blockout members of FIG. 6.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawing and will herein be described in detail an embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring to FIG. 1, a computer control center C includes a pushbutton assembly, generally designated PBA, which comprises the keyboard portion of the control panel for the computer. Such an assembly may be used to operate electrical switches which either feed information to or request information from the computer. The assembly is commonly called a bank of pushbuttons. One aspect of the blockout mechanism of this invention is particularly adapted for use with such banks.

Referring to FIGS. 2 through 4, the pushbutton assembly includes a plurality of adjacent rows R of pushbuttons 10, each button operating a pushrod 12 for reciprocating movement toward and away from a supporting means which mounts the same. FIGS. 2 and 3 show a single row of five pushbuttons. FIG. 4 is an end view of an assembly having five adjacent rows R of pushbuttons. Obviously, a greater number of pushbuttons or rows may be employed, with the maximum limit being governed by the accumulated tolerance of the blockout members (as hereinafter described). The pushrods may operate electrical switches in a manner well known in the art and which will not be described in detail herein. The pushbuttons are normally in an elevated inoperative po sition, as shown in FIGS. 2 and 4. On depressing a pushbutton (FIG. 3), an electrical switch is actuated to produce the desired results.

The supporting means illustrated in the drawings is comprised of a front or a top supporting plate 14 and a rear or bottom supporting plate 16 secured together in a spaced generally parallel relationship by end supporting plates 18. The pushrods reciprocate through appro priate apertures in the top and bottom plates 14 and 16, respectively, to actuate appropriate switches. As best seen in FIG. 5, a coil spring 20 embraces a center leg portion 22 of each pushrod 12 and is compressed between the bottom support plate 16 and a projection 24 extending laterally away from the pushrod. The compressed coil spring 20 normally urges the associated pushrod, and their respective pushbuttons, toward an elevated inoperative position.

The blockout mechanism includes a row of first blockout slider members 26 (FIGS. 2 and 3) for each row R of pushbuttons and pushrods. The blockout sliders 26 are slidably received in a row in a closed end channel member 28 which is secured to the underside of the bottom support plate 16. Referring to FIG. 5, each row of first sliders 26 is positioned in the path of movement of, and engageable by, a side leg portion 30 of each push rod 12 in each respective row of pushbuttons. The sliders are provided with camming surfaces 31a (FIG. 6) in the path of movement of the side leg portions 30 of the push rods 12. As a pushbutton is depressed, depressing the respective pushrod 12, the respective leg portion 30 engages the camming surfaces 31a of the subjacent sliders and moves the sliders to the side so that the push rod can continue its downward movement to actuate the appropriate switch. The total clearance between all of the sliders 2 6 of each row thereof is less than two times the width of a single pushrod portion 30 to permit only one push rod (and therefore only one pushbutton) in a single row to be fully depressed at a time.

Each row of pushbuttons is provided with a common depressible connecting means mounted on the underside of the bottom support plate 16 independently of the first sliders. The connecting means for one row of pushbuttons includes two angle brackets 32 (FIGS. 2 and 3) one mounted at each end of each row of pushrods on the underside of the bottom support plate 16 and bell cranks 34 pivotally attached to the downwardly depending portion of each angle bracket by rivets 34a. Each bell crank has a horizontal leg 35a and a vertical leg 35b. A blockout treadle bar 36 is pivotally secured, as by rivets 37, to the horizontal legs 35a of the bell cranks 34. The treadle bar is horizontally disposed in the path of movement and engageable by the center leg portion 22 of each pushrod (FIG. 5) of each respective row. A link bar 40 is pivotally secured to the vertical legs 35b of the bell cranks 34 to maintain the treadle bar 36 horizontally disposed at all times. Because of the link bar 40 and bell cranks 34, if a pushbutton is depressed, the entire treadle bar 36 is depressed in a constant horizontal progression rather than merely being depressed at the right end of the treadle bar (which is beneath the pushbutton 10', for instance). A coil spring 42 (FIG. 3) is mounted at its upper end. to the top supporting plate 14 and at its lower end to the treadle bar 36 to maintain the treadle bar in an elevated position when not depressed by a pushrod. Each treadle bar has a plunger portion 44 at its left end in FIG. 3 Which engages a row of second blockout slider members 46, similar to the slider members 26. The second sliders 46 are slidably received in a closed end channel member 48 which is mounted on the underside of the bottom support plate 16 independently of the first sliders 26.

The row of second sliders 46 is positioned in the path of movement of, and engageable by, the plunger portion 44 of each depressible treadle bar 36. The total clearance between the second sliders is less than two times the width of a single plunger 44 to permit only one treadle bar at a time to be fully depressed and therefore to prevent any two pushbuttons in any two ditferent rows thereof from being depressed at a single time. It can be seen that the row of sliders 46 perform a universal function and cooperate with the sliders 26 in each row of pushrods to prevent any two pushbuttons in the entire bank from being depressed at one time. This is accomplished because any two pushrods 12 in a single row R cannot simultaneously bypass sliders 26 while any two treadle bars (and its plunger 44) in any two rows are prevented from bypassing sliders 46.

It can be seen that by eliminating any linkage between and completely divorcing the universal row of sliders 46 from the individual rows of sliders 26, the only limitation on the number of pushbuttons available in a bank is the accumulated manufacturing tolerance of the sliders in a single row. Since there is no interaction between the rows, there is no multiplication of the tolerances between any two rows.

In the conventional blockout system, balls or rollers are employed wherein adjacent rollers abut one another and are pushed aside as a push rod is depressed therebetween. The total tolerance permissible (in addition to the required clearance for one pushrod) in such conventional blockout members is the thickness of a single push rod. In order for two pushrods to be depressed in such assemblies, the rollers must be displaced twice the thickness of the pushrod.

Referring to FIGS. 6 and 7, the slider members 26 and 46 have a novel design which increases the permissible accumulated tolerance of the sliders. The ends of adjacent sliders overlap and thereby increase the permissible accumulated tolerance in any single row of sliders. In the embodiment illustrated, the amount of overlap is approximately the thickness of a pushrod portion 22 and thus the sliders must be displaced twice the thickness of the portion 22 in order for a single pushrod to be depressed. Therefore, for any two pushrods to be depressed at a single time, the slider must be displaced four times the thickness of portions 22, thus doublin g the permissible accumulated tolerance over the conventional abutting cam members.

FIGS. 4 and 5 best illustrate the means by which an individual pushbutton is locked in its depressed position and the means by which such a locked button is released on depressing a successive button. A vertically disposed latch plate 52 (FIGS. 2 and 3) is provided for each row of buttons and is pivotally mounted at points 53 to the end support plate 18 and has an inwardly curved lip 54 (FIG. 5) along its lower edge. The side leg portion 30 of each pushrod 12 is provided with a recess 56 for receiving the lip 54 when the pushbuttons are elevated. All of the latch plates 52 are linked together by a link bar '58 (FIG. 4) andare urged into the recesses 56 of each pushrod portion 32 by a latch spring 60. The spring is attached to a fixed supporting projection 62 and is secured to the left hand side of the link bar 58. Referring to FIG. 5, as a pushrod 12 is depressed, its respective latch plate 52 is urged outwardly as shoulder 64 of recess 56 bears against the latch plate lip 54. A locking notch 66 is cut into the pushrod portion 30 at a position where it will receive lip '54 of the latch plate and lock the pushrod when the appropriate electrical switch is actuated. Latch spring 60, acting through link bar 58, will urge the latch plate 52 into the notch 66 on the pushrod portion 30 and lock the pushrod in its depressed position. When another pushbutton is depressed, shoulder 64 on its pushrod portion 30 will urge the latch plate outwardly out of the locking notch 66 of the previously depressed pushrod, thus releasing the previously depressed pushbutton. Further movement of the second pushbutton will lock the latch plate 52 in its respective locking notch 66 as above described. It is desirable that the shoulder 64, 'which releases the latch plate, be spaced a suificient distance from the locking notch 66 so that the release of a depressed button does not necessarily result in the locking of any other button, so that all pushbuttons may be maintained in their elevated inoperative position if desired.

I claim:

1. In a pushbutton assembly having a plurality of adjacent rows of pushbuttons each operating a pushrod for movement toward and away from a supporting means which mounts the same, a blockout mechanism, comprising: a row of first blockout members for each row of pushrods and mounted on said supporting means in the path of movement of and engageable by a portion of each pushrod of each respective row, the total clearance between said first blockout members of each row thereof being greater than the width of one and less than the width of two pushrod portions to permit only one push-button in a single row to be fully depressed at a time; a connecting means for each row of pushrods and mounted on said supporting means in the path of movement of and en'gageable by a portion of each pushrod of each respective 'row, so that the depression of any pushbutton in any single row will cause its respective pushrod to engage and move the respective connecting means; and a row of second blockout members mounted on said supporting means independently of said first blockout members and in the path of movement of and engageable by a port-ion of each said connecting means, the total clearance between said second blockout members being greater than the width of one and less than the width of two connecting means to permit only one connecting means to be moved at a time, whereby said row of second blockout members, said connecting means for each row of pushrods, and said rows of first blockout members cooperate to permit only one pushbutton in said pushbutton assembly to be fully depressed at a time.

2. The pushbutton assembly of claim 1 including a spring means to urge said connecting means to an inoperative position when not engaged by a pushrod.

3. The pushbutton assembly of claim 1 wherein said connecting means includes an elongate treadle bar engageable by a portion of each pushrod of each respective row, said treadle bar being swivelly mounted to said supporting means so that the treadle bar moves in a plane parallel to the motion of said pushrods.

4. The pushbutton assembly of claim 3 including means for maintaining the treadle bar horizontal at all times.

5. The pushbutton assembly of claim 4 wherein said means for maintaining the treadle bar horizontal includes bell cranks pivotally secured to said supporting means adjacent each end of said treadle bar, each bell crank having a first leg pivotally mounting said treadle bar at opposite ends thereof and a second leg angularly disposed from said first leg, and an elongate link bar pivotally secured at opposite ends to the second legs of said bell cranks.

6. In a pushbutton assembly having a plurality of groups of pushbuttons each operating a pushrod for movement toward and away from a supporting means, a blockout mechanism, comprising: a first blockout means for each group of push rods to permit only one pushbutton in a single group to be fully depressed at a time; a connecting means for each group of pushrods and means for actuating the connecting means when a pushbutton is depressed in the respective group; and a second blockout means independent of said first blockout means to permit only one connecting means to be actuated at a time, whereby said first blockout means, said connecting means and said second blockout means cooperate to permit only one pushbutton in said pushbutton assembly to be fully depressed at a time.

7. In a pushbutton blockout mechanism, a row of pushbuttons each operating a pushrod, a row of blockout members for said row of pushrods, the blockout members being positioned end-to-end and permitting only one pushnod "to be operated at a time, each blockout member having an abutting surface which overlaps with the abutting surface of each adjacent blockout member.

8. The blockout mechanism of claim 7 wherein said blockout members include a plurality of sliders slidably received in a channel member, said sliders being disposed in the path of movement of a portion of each pushrod in said row thereof, each slider having a camming surface opposing the camming surface of adjacent sliders, each of said opposed camming surfaces being positioned for engagement by one said portion of one of said pushrods.

References Cited UNITED STATES PATENTS 2,192,621 3/1940 Radtke 74483 XR FRED C. MATTERN, JR., Primary Examiner.

F. D. SHOEMAKER, Assistant Examiner. 

